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Welcome to the website of Nicole and Renato Bender.

This site is intended to provide a source of information on several topics around evolutionary biology. Beside our works on evolutionary medicine, behavioral ecology and history of science, the main aspect of our research concerns primates’ interaction with water, with special focus on early hominin evolution.

Hominiods’ interaction with water: an understudied field in primatology

Extant hominoids (gibbons, orangutans, gorillas, common chimpanzees, bonobos and humans) are very interesting organisms in their behavior toward water. Although swimming is a widespread, crucial behavioral feature among mammals, non-human hominoids are believed to be unable to cross a deep water body. As a general rule, humans are the only extant hominoids which interact with water in a way that regularly (but not necessarily) leads to the development of swimming ability. Considering this fact, it is remarkable that hominins’ interaction with water is such an understudied topic in paleoanthropology.

There are several reasons for this neglect. Classical scenarios on early hominin evolution usually did not consider the possibility that hominins evolved specific behavioral, anatomical or physiological features related to any form of intensive water use. In paleoanthropology, human swimming and diving are implicitly considered a modern achievement in our evolution and are therefore normally not analyzed from an evolutionary point of view. For this reason, the history of human swimming and diving ability is classically treated by historians who restrict their analysis on data which can be documented by archeological evidence, as in the Stone Age paintings or written references (like the Bible).

The probable most important reason for the lack of scientific paleoanthropological research on hominins interaction with water is related to the aquatic hypotheses, also called the aquatic ape theory. The simple mention of the “role of water in early hominin evolution” inevitably brings out strong feelings related to these controversial ideas. The aquatic hypotheses were independently proposed by the German pathologist Max Westenhöfer (1871-1957) and the British marine biologist Sir Alister Hardy (1896-1985) and since 1972 continuously propagated by the British writer Elaine Morgan (born 1920). They defend the idea that early hominins developed several anatomical, physiological and behavioral characteristics in connection with a semi-aquatic environment. The most common version of the aquatic hypothesis was formulated by Alister Hardy in an article in New Scientist on March 17, 1960. He wrote:

“My thesis is that a branch of this primitive ape-stock was forced by competition from life in the trees to feed on the sea-shores and to hunt for food, shell fish, sea-urchins etc., in the shallow waters off the coast. I suppose that they were forced into the water just as we have seen happen in so many other groups of terrestrial animals. I am imagining this happening in the warmer parts of the world, in the tropical seas where Man could stand being in the water for relatively long periods, that is, several hours at a stretch.”

These hypotheses have not been accepted within the paleoanthropological community as valid scenarios for early hominin evolution. The emotional discussion surrounding the aquatic hypotheses had a negative influence for decades on how researchers approached the topic of primates’ interaction with water. There is a general unspoken agreement among paleoanthropologists that discussing hominins’ interaction with water is analogous to entering a scientific minefield.

A research program without the usual discussion “Aquatic Ape Theory against Savanna Theory”

Scientists interested in primates’ interaction with water and it’s implication for early hominin evolution probably feel uneasy envisioning themselves submerged in the extensive research necessary to understand in depth the intricate arguments of the proponents of the aquatic hypotheses in the last 88 years. Such a project becomes even less attractive considering that most of the aquatic ideas were not formulated in peer reviewed literature by specialists, but in popular articles and books written by non-specialists. Attempts to overcome these problems by giving the aquatic hypotheses a new name and ignoring the historical roots of these ideas only contributes to increasing rather than reducing the chaos in this field.

However, several paleoanthropologists probably would like to discuss the role of water in early hominin evolution without being regarded as proponents or critics of the aquatic hypotheses. In fact, there are many good reasons to put an end to this discussion as it has been carried out in recent decades (in the sense of “Aquatic Ape Theory against Savanna Theory”) and to start a new research program in paleoanthropology. Instead of discussing the sense or nonsense of highly speculative ideas (for instance when comparing humans with penguins or with dolphins), we propose a research program addressing water use in primates, which by definition include hominins.

It is important to point out that the expressions “water use” or “interaction with water” in connection with early hominins does not necessarily imply the evolution of specific adaptive features in these species in the sense of “aquatic” adaptations. (For example, one topic of our research on primates’ interaction with water is the avoidance of water bodies by several primate species.) This approach prevents the bias related to the discussion of a few single scenarios and avoids ineffective research that overlooks relevant data.

We propose therefore three strategies to use with the topic “water use in early hominins”.

Historical analysis

The first strategy is to make an objective analysis of the historical roots of hypotheses that contextualize early hominin evolution. On this webpage are the summaries of two German theses and papers on this topic. (For German-speaking scientists the PDFs of the original works are included.) and papers. To illustrate a typical pitfall arising from superficial assumptions characterized by a lack of historical understanding, one author believed it was possible to identify exactly the historical influences which led to the formulation of Hardy’s aquatic hypothesis first published in 1960. These assumptions cannot hold because Hardy did not envisage his ideas in 1960, but much earlier. Furthermore, the same arguments were proposed by Max Westenhöfer 37 years before Hardy’s first aquatic hypothesis publication. It is apparent that the Zeitgeist and specific scientific background that influenced Hardy’s ideas were not comparable to the influences which led to Westenhöfer’s Aquatile Hypothese.

Similarly, several scientists mentioned Raymond Dart as first author of the classical savanna hypotheses (SHs). According to this scenario, climatic changes thinned forest areas and caused the appearance and extension of open plains, forcing early hominins to adapt to new conditions of life. A review of the topic reveals that the first SHs did not emerge as an interpretation of hominin fossil evidence discovered in Africa in 1924 by Raymond Dart, as commonly assumed. Open plains ideas were already outlined in 1809 by Jean Baptiste de Lamarck and 1871 by Charles Darwin, and several detailed SHs were published in the two first decades of the 20th century. Although still very influential in paleoanthropology, the savanna scenarios have been challenged since the early 1990s by several paleoanthropologists and primatologists (Bender 1999; Bender, Tobias and Bender submitted a paper on this topic).

The rational for considering historical research is simple: it is impossible to make inferences about the validity of hypotheses without a profound understanding of their arguments seen from an historical perspective. It is remarkable that the long and heated debate over “aquatic ape theory versus savanna theory” could be carried out with such a lack of basic knowledge of the historical development of these ideas. (See for instance the several wrong statements on the history of the aquatic hypothesis and savanna hypothesis in the English Wikipedia.)

Analysis of approaches and theoretical concepts

The second strategy concerns an objective evaluation of the approaches and theoretical concepts used in the different hypotheses proposed to contextualize early hominin evolution. (This strategy also demands extensive historical analyses, since several of the approaches and scenarios used in paleoanthropology to date have their roots in ideas already proposed in late 19th and early 20th centuries.)

This analysis is a very complex task. It is, of course, much simpler to develop a new method to corroborate another hypothesis on early hominin evolution than to get involved in an arduous and time-consuming analysis of previous methods used to corroborate a vast number of scenarios proposed in paleoanthropology. Nevertheless, we assume that such an analysis is indispensable in any attempt to test the validity of single paleoanthropological hypotheses. Especially important is the analysis of approaches addressing the use of convergences as a tool in the analysis of adaptive features (see “human evolution / convergence approach”), since this is the most basic aspect implicit in several influential scenarios on early hominin evolution.

Focusing on empirical evidence when it is available

We emphasize the need for empirical evidence related to primates’ interaction with water. In times when young scientists feel that progress in evolutionary biology is only possible through detailed work within established research programs, it is refreshing to note that the gathering of empirical data concerning primates’ interaction with water allows not only some spectacular discoveries even on species believed to be extremely well studied, but also the beginning of new research programs.

For instance, it is believed that non-human hominoids are unable to swim. We are preparing papers with the first descriptions of the swimming and diving abilities of five different individuals (4 common chimpanzees, 1 orangutan) which revise the allegedly fundamental difference between humans and non-human hominoids concerning their interaction with water. For the first time it is possible to compare swimming movements, behavior under water, breath-control and diving response between different non-human hominoids and humans. See further information on page “Human evolution / primates’ interaction with water”.

This website among others will be regularly updated in the upcoming months with references to our scientific publications in preparation.